I'm from Sacramento (so I know Davis) and I'm a current student at UCSC.
COME TO SANTA CRUZ. The school is amazing- I love all my classes (I'm a history/politics guy, but my science/engineering friends say the same), and the people are fantastic. Seriously- Davis is full of boring, high school-caliber boring frat people. Also, Davis is really, really lame. There's always something going on in SC- concerts, events, whatever. Far more laid back, the people are infinitely cooler, etc., ad nauseum. Also, there's actually some politically active people here, which is far more than you can say for 99.6% of the rest of the country (especially including Davis).
edit: if you have any specific questions, id be happy to answer them.
oh, and don't go by the tour here- it's the most idiotic thing ever. After I visited, Santa Cruz was my last choice, but after a year and half here, I am SO, so glad I ended up (read: was rejected from everywhere) here. It's pretty much a perfect fit.
I think the best thing about this place is the atmosphere. It's exactly as intense as you want it to be. I'm taking some pretty hard classes, so I'm busy all the time with work, but I love all of it. I definitely know some people who just skate by, but they'll never know what they're missing. The point is that there's very little competitiveness around here, which is pretty much the best thing in the world.
Also, the only frats are the ethnic ones, the Jew one, and the gay one, and they're all off-campus, so they don't really exist. There are very few (you can find them if you want them, but they're definitely the minority) huge, kegger-type crazy-ass parties that go on- much more of the laid-back, you'll-know-everyone-there type of things. far superior party scene, IMO. also, no one pays any attention to sports (we don't have a football team, for example- but we've got pretty decent teams of most everything else, so i hear), which is awesome.
...and ok, that's enough procrastinating and not writing my paper. good luck, and come to Santa Cruz.